What sort of aluminium panel? Is its just a plain sheet or something like ACM?
Normally, cladding panels are part of a system, and have proprietary support channels or brackets. And there would be a drained and ventilated cavity.
Or, you would use fixings with a plastic or EPDM spacer. Or timber battens fixed with hilti nails.
This is really something that your plan drawer should properly detail. You have a few things going on there that need thinking about, not just fixing.